The present disclosure relates to platinum nanoparticles. More particularly, the present disclosure relates to stabilized platinum nanoparticles used as a catalyst in a fuel cell.
Platinum nanoparticles are well known for use as an electrocatalyst, particularly in fuel cells used to produce electrical energy. For example, in a hydrogen fuel cell, a platinum catalyst is used to oxidize hydrogen gas into protons and electrons at the anode of the fuel cell. At the cathode of the fuel cell, the platinum catalyst triggers the oxygen reduction reaction (ORR), leading to formation of water. The ORR reaction takes place at high potential, which makes the platinum nanoparticles unstable on the cathode, resulting in a loss in electrochemical surface area of the nanoparticles. Due to potential cycling during fuel cell operation, the platinum nanoparticles may dissolve. The atoms at the corners and the edges of the nanoparticles have a higher surface energy and, as such, are more reactive than surface atoms on the terraces of the nanoparticles. The nanoparticles commonly include surface features or defects that form on the surface during synthesis of the nanoparticles. The atoms that form these surface defects, including steps and kinks, are also more reactive sites on the nanoparticle, compared to the surface atoms on the terraces. The more reactive atoms are more prone to dissolving and forming oxides, as compared to atoms having lower surface energy.
Although platinum is a preferred material for use as a catalyst in a fuel cell, platinum is expensive. Moreover, the instability of the platinum nanoparticles in the cathode environment results in a loss of surface area of the nanoparticles, and consequently a loss in fuel cell performance. This requires a larger amount of platinum catalyst to be used in the fuel cell, which increases cost. There is a need for a platinum nanoparticle that is more stable during operation as a cathode catalyst in a fuel cell.